Correspondence

The answer was directly in front of our eyes. Or actually it wasnot, because every artificial sweetener suddenly disappeared fromour ward from the day of the patient’s admission. Thoroughanamnesis showed daily consumption of 1 box (600 sachets) of acommon artificial sweetener and 3 L of Diet Coke. Saccharin andcyclohexylamine, a metabolite of cyclamate, initially were detect-able using high-performance liquid chromatography in plasma anddisappeared after withdrawal of the sweetener; subsequently, therewas normalization of plasma osmolality and urine volume.

The present case shows that artificial sweeteners and theirmetabolites are osmotically active compounds. Furthermore, itshows that plasma osmolal gap is a useful tool to distinguishendogenous and exogenous solutes in osmotic polyuria (Fig 1).

Felix S. Seibert, MD1

Benno Riesselmann, MD2

Timm H. Westhoff, MD1

1Charité–Campus Benjamin Franklin2State Institute of Legal and Social Medicine

Berlin, Germany

AcknowledgementsThe corresponding author, Dr Westhoff, may be contacted at

timm.westhoff@charite.de.Support: None.Financial Disclosure: The authors declare that they have no

relevant financial interests.

Reference1. Dashe AM, Cramm RE, Crist CA, Habener JF, Solomon DH.

A water deprivation test for the differential diagnosis of polyuria.JAMA. 1963;185:699-703.

© 2011 by the National Kidney Foundation, Inc.doi:10.1053/j.ajkd.2010.11.016

Obstruction of a Peritoneal Dialysis Catheter by anOvarian Fimbria in a 2-Year-Old GirlTo the Editor:

Laparoscopy of a nonfunctioning peritoneal dialysis (PD) cath-eter in a 2-year-old girl receiving continuous ambulatory PDshowed it to be blocked by an ovarian fimbria of the left fallopiantube. The fimbriae were repositioned and the catheter starteddraining well. The problem recurred within a week and repeatedlaparoscopy showed the catheter to be blocked once more by thefimbria. This again was freed and normal drainage was restored,but it started malfunctioning after a month. Laparoscopy again

Non-osmo�c diuresis

Urine osmolality< 300 mosm/kg

Waterrestric�on test:Urine osmolality < 300

mosm/kgPlasma osmolality > 300

mosm/kg

Waterrestric�Plasma osmola

normal rang

Psychogenic PolyDiabetes insipidus

Figure 1. Simplified diagnostic approach to polyuria. The ursolutes in osmotic polyuria. Definitions based on Dashe et al.1

showed recurrence of the problem along with appendices epiploi-

356

cae obstructing some of the other catheter holes. In addition,necrotic debris, probably secondary to necrosis of either theovarian fimbria or appendices epiploicaes, also were obstructingthe catheter lumen (Fig 1). In view of repeated obstruction of thecatheter and the patient’s dependence on PD therapy, a partialfimbriectomy was undertaken after consultation with the entiremedical team and parents. One year later, the PD catheter contin-ues to function well.

Although obstruction of a PD catheter by an ovarian fimbria hasbeen reported, a MEDLINE search showed only a single previousreport in children.1-3 Fimbriectomy to prevent recurrence of PDcatheter obstruction can be an option in the elderly,4,5 but needs tobe discussed fully and debated in children. This report highlightsthe need to be aware of this unusual cause of catheter blockageeven in children, as well as the ethical problem of balancing therisk of future infertility with possible discontinuation of a life-sustaining procedure in a young girl.

Rajiv Sinha, MD, FRCPCH CCT (Paed Nephrology)AMRI Hospitals

Kolkata, India

Arindam Dastidar, MS, Mch (Paediatric Surgery)Christian Medical College

Vellore, India

AcknowledgementsThe corresponding author, Dr Sinha, may be contacted at

rajivsinha_in@yahoo.com

Osmo�c diuresis

Urine osmolality> 300 mosm/kg

:

Endogenous solutes,eg, hyperglycemia

Osmolal gap< 10 mosm/kg

Osmolal gap> 10 mosm/kg

lyuria

solutesExogenous

smolal gap differentiates between endogenous and exogenous

Figure 1. Image shows (A) ovarian fimbria and (B) appendi-

on testlity in

e

Po

dipsia

ine o

ces epiplocea blocking the holes in a peritoneal dialysis catheter.(C) Necrotic debris is visible in the lumen.

Am J Kidney Dis. 2011;57(2):352-359

Correspondence

Financial Disclosure: The authors declare that they have norelevant financial interests.

References1. Abidin MR, Spector DA, Kittur DS. Peritoneal dialysis

catheter outflow obstruction due to oviductal fimbriae: a casereport. Am J Kidney Dis. 1990;16(3):256-258.

2. Moreiras-Plaza M, Cáceres-Alvarado N. Peritoneal dialysiscatheter obstruction caused by Fallopian tube wrapping. Am JKidney Dis. 2004;44(2):e28-30.

3. Borghol M, Alrabeeah A. Entrapment of the appendix andthe fallopian tube in peritoneal dialysis catheters in two children.J Pediatr Surg. 1996;31(3):427-429.

4. Klein Z, Magen E, Fishman A, Korzets Z. Laparoscopicsalpingectomy: the definitive treatment for peritoneal dialysiscatheter outflow obstruction caused by oviductal fimbriae. J Lapa-roendosc Adv Surg Tech A. 2003;13(1):65-68.

5. Uchiyama K, Fujikawa K, Suga A, Naito K. Laparoscopicsalvage of malfunctioning peritoneal dialysis catheters caused byovarian fimbria: a case report. Hinyokika Kiyo. 2001;47(9):669-671.

© 2011 by the National Kidney Foundation, Inc.doi:10.1053/j.ajkd.2010.11.017

RESEARCH LETTER

Sevelamer Prescriptions After Reportingof the Dialysis Clinical Outcomes Revisited(DCOR) Trial Findings: An Analysis of 5,495Patients Receiving Maintenance Dialysis inOntario, CanadaTo the Editor:

A randomized controlled trial (RCT) often is accepted as thebest way to test the effects of a therapy. When an RCT shows asignificant benefit or harm, the findings can readily translateinto clinical practice.1-3 However, predicting the effect of anegative trial (one that fails to show statistically significantresults) is more problematic. We recently showed that 4D (DerDeutsche Diabetes Dialyse Studie), a negative trial of atorvasta-tin in dialysis patients, was not associated with a change in theuse of statin drugs in this population.4 We speculated thatanother negative study, the DCOR (Dialysis Clinical OutcomesRevisited) trial,5 also might have failed to influence sevelameruse in dialysis patients and therefore examined the rate ofsevelamer prescriptions before and after reporting of DCORresults.

Using Ontario’s health administrative data, we conducted aretrospective interventional analysis from January 1, 2001, toMarch 31, 2009. Ontario is Canada’s most populous province,with approximately 13 million residents who receive universalhealth coverage under the Ontario Health Insurance Plan (OHIP).Beginning in 2001, prescription drug coverage for sevelamerwas provided at a physician’s request to any patient withend-stage renal disease who on 2 occasions had serum calciumand phosphate concentrations �2.65 and �1.80 mmol/L, respec-tively, despite using a calcium-based binder. We determined thenumber of quarterly sevelamer prescriptions using the OntarioDrug Benefits (ODB) database, which has an error rate of�1%.6 We assembled a cohort of patients receiving mainte-nance dialysis using billing codes recorded in the OHIP data-base (Item S1, available as online supplementary material). Toascertain prescription drug use from the ODB database, we

limited our cohort to patients 66 years or older. We excluded

Am J Kidney Dis. 2011;57(2):352-359

cases of dialysis for acute kidney injury. Patients were removedfrom the cohort at the time of kidney transplant or death. Withinthis cohort, we determined the numbers of sevelamer prescrip-tions per 1,000 dialysis patients each quarter for 33 quarters.

Reporting of DCOR results at the American Society ofNephrology annual conference in November 2005 was ourintervention of interest. DCOR was a prospective multicenteropen-label RCT comparing sevelamer with calcium-based phos-phate binders in 2,103 patients receiving maintenance hemodi-alysis. The investigators aimed to show reductions in all-causeand cardiovascular mortality, but after 45 months of follow-up,no significant differences in these outcomes were found.5 Al-though presented first in November 2005, the trial was pub-lished in November 2007, with a secondary analysis publishedin March 2008.5,7 To assess for a change in sevelamer prescrip-tion rate after the reporting of DCOR, we applied an autoregres-sive integrated moving average model–based intervention anal-ysis to a time series of sevelamer prescriptions per 1,000patients. As a tracer outcome, we assessed the calcitriol prescrip-tion rate within the cohort, expecting that DCOR results wouldhave no impact on calcitriol prescriptions. During the 8-yearstudy period, our cohort grew from 3,528 to 5,495 patients.Table 1 lists baseline characteristics of patients enrolled inDCOR and those in our cohort. Overall, Ontario patients wereolder, less likely to have diabetes, and on dialysis therapylonger. The intervention analysis showed a significant change insevelamer prescription rate after the reporting of DCOR (Fig 1;P � 0.01). A significant change in prescription rate of the tracerdrug calcitriol was neither expected nor observed.

After DCOR results were reported, we observed a sudden haltin the increasing number of sevelamer prescriptions filled byelderly patients on dialysis therapy. We suspect that physiciansresponded strongly to the results of DCOR for a number ofreasons. First, this finding may reflect physicians’ appropriatelycautious interpretation of the subgroup analysis that suggestedimproved mortality rates in patients older than 65 years.5,7,8

Second, there were no mortality data from other studies torefute DCOR’s findings. Third, inexpensive and effective alter-native medications were readily available to treat hyperphos-phatemia. Finally, unlike statins, no evidence outside the end-stage renal disease population existed to support the use ofsevelamer.

Our study examined a large cohort of patients and ascertainedprescriptions and comorbid conditions using validated codesand reliable databases.6,9 However, our cohort was not perfectlyanalogous to the patients enrolled in DCOR. Although therewere no changes to funding for sevelamer or the procurement

Table 1. Baseline Characteristics of Patients in the DCOR Trialand Ontario Cohort

DCOR Ontario Cohorta

Sample size 2,103 5,495

Age (y) 60 � 15 76 � 7

Women (%) 45.6 43.6

Diabetes mellitus (%)b 50.2 38.0

Dialysis duration (mo) 38 � 40 50 � 46

Note: Values expressed as mean � standard deviation orpercentage unless stated otherwise.

Abbreviation: DCOR, Dialysis Clinical Outcomes Revisited.aBaseline characteristics were determined using the most

recent quarter of data (January 1, 2009, to March 31, 2009).bFor Ontario data, the diagnosis of diabetes mellitus was

determined using valid health administrative codes.

357